1. Effects Menu

      2. After you've stored the audio signal onto your computer hard disk, what can you do with it? Well, just as a word processor lets you manipulate the words and pictures that make up a document, VFEdit® lets you edit sound in much the same way. You can make a sound "bold" by increasing its volume; make it "italic" by changing the pitch.

      The Effects Menu lets you work on the original sound recording and make it fancier. With Effects Change Frequency, you can change the frequency it is recorded in. With Effects Echo, you can sound as if you are talking in a huge sound-reflective room. You can Fade In or Fade Out certain words, Mix in music from other files, submit the whole palette of frequencies to an Equalizer, or adjust the volume of the stored sound file with Volume Up, Volume Down, and Normalize. You also can edit out background hiss with Reduce Noise or improve the depth and range of the voice quality with Effects Dynamic Compress/Expand. In short, the Effects Menu lets you create files that sound like you hired a professional sound studio to help you make a tape.

      You can change the default effects parameters using the "Effects Configure" menu command described later in this document. The following discussion assumes that you are using the default VFEdit effects parameters.

      1. When Would You Use Effects?

        2. Imagine you have a travel agency. You want your voice system to call your clients, promote a week in Hawaii, and play some exotic Hawaiian hula music to set the scene. (Studies have shown that adding music to an audio phone message can increase retention level by as much as 30%.) With just a few mouse clicks you can mix that music into the background of your sales pitch.

      2. Selecting Audio Segments

Selecting audio segments is how you focus the editor's attention on the sound segment you want to edit, like shining a flashlight or a spotlight on it. You can use the mouse or the keyboard to specify the beginning and ending of an audio segment. VFEdit gives you several ways to make this selection:

    1. With the mouse, create a dashed box around the audio graph.
    2. Use Edit Select All.
    3. Use Edit Select Extents.
    4. Select "Whole File" from the Options Environment Menu.
    5. Select "Ask User" from the Options Environment Menu.

Use the mouse to select an audio segment by first positioning the mouse at the point of interest displayed on the screen. Then press and hold the mouse button while moving the mouse to the end of the segment. A dashed box will enclose the area you have selected. Release the mouse button.

If you have not selected a segment for editing by using the mouse, and you have selected "Ask User" from the Options Environment Menu, VFEdit automatically displays a dialog box that lets you specify the beginning and ending portion of the file (in seconds) that you wish to edit. Time may be specified to 1/100th of a second accuracy.

If you have not selected a segment for editing by using the mouse, and you have selected "Whole File" from the Options Environment Menu, VFEdit will automatically select the whole file.

If you choose Edit Select Extents from the menu bar, VFEdit will display a dialog box that lets you specify the beginning and ending portion of the file (in seconds) that you wish to edit. If you choose Edit Select All from the menu bar, VFEdit will automatically select the whole file.

You can stretch or shrink the box around a previously selected audio segment by first positioning the mouse at the edge of the dashed boxed. Notice that the mouse cursor changes shape to a right/left arrow. Press and hold the mouse button while moving the mouse to the new position of interest. You can clear a previously selected segment by pointing and clicking the mouse at any point away from the edge of the selection box.

Once you have a sound segment "selected" or "highlighted", you use any of the Effects Menu commands, or use control buttons on the toolbar.If you select an audio segment that extends past the end of the file, VFEdit automatically resets the segment end point to the total length of the file for all Effects operations.

      1. Effects Change Frequency

        2. Effects Change Frequency lets you change the pitch and speed of a recording. Changing by values greater than 100% will increase the pitch and speed up the audio. Changing by values less than 100% will decrease the pitch and slow down the speed of the audio.

        Use Effects Change Frequency command when you have a recording that was produced on hardware set for a different sampling frequency, or if you want to make a voice sound higher or deeper.

        The "Multiply by %" parameter lets you increase (greater than 100%) or decrease (less than 100%) the pitch and speed of the audio.

      2. Effects Dynamic Compress/Expand

        3. Effects Dynamic Compress/Expand lets you improve dynamic range of the audio. The dynamic compressor/expander works by analyzing the audio signal and increasing the volume level on sections that are too soft while decreasing the volume level on sections that are too loud.

        Use this command to improve the "depth" and "range" of the recorded voice.

      3. Effects Echo

        4. The Effects Echo command is used to permanently add echo to the stored audio data. Adding an echo to a sound segment will make it sound more melodious and resonant. Use Effects Echo to add depth to a voice recording. For example, many vocalists add a small amount of echo to their voice to improve the sound. Add a larger amount of echo to liven your recordings with a "hall-like" ambiance. Add an even larger amount of echo to produce chorus effects.

        When you select Effects Echo, VFEdit mixes a delayed portion of the recorded audio with the current sound. The delay time and attenuation level are specified using the Effects Configure menu. These parameters determine how far behind the original the echo will come, and the factor for the volume decay. They are expressed in seconds and decibels respectively.

        Technically speaking, Effects Echo attenuates audio samples (as specified by the decay parameter) from a prior time (as specified by the delay parameter) and mixes them with the current sample.

      4. Effects Equalize

The Effects Equalize command lets you fine tune the sound of your words, to change the quality of the vibrations themselves. While a microphone records the whole range of vibration in sound levels, the equalizer can be used to make certain ranges softer and other ranges louder, so that the net effect makes you sound different.

When you select Effects Equalize, you will be presented with a dialog box that lets you adjust the relative levels of frequency bands. By moving the controls up or down from the center point, you will increase or decrease the volume level of the audio in those frequency bands. After adjusting the frequency band controls, press "Equalize" to apply the changes to the recorded audio.

When you select Effects Equalize, you will be presented with a dialog box that lets you display the current frequency content of the audio file. Press the "Show" button to see a three-dimensional representation of the frequency spectrum.

The icon bar on the Frequency Spectrum Analyzer also enables you to:

Copy Spectrum Analyzer image to the clipboard as a bit map.
Change the color displayed for various frequency levels.
Switch between 3-D and 2-D views
Rotate the chart.
Zoom in and out.
      1. Effects Fade In, Out

        2. The Effects Fade In menu command is used to permanently change the volume level of the stored audio data. Effects Fade In gradually increases the volume level from a specified low volume point to a specified final volume point. This adjusts the amplitude of the sounds so that the volume is higher and increasing toward the end of the selected audio segment.

        Effects Fade Out gradually decreases the volume level from a specified high volume point to a specified final volume point. This adjusts the amplitude of the sounds, so that the volume decreases toward the end of the segment.

        Technically speaking these commands increase (or decrease) the signal power level linearly over time. Note that VFEdit varies the signal power level, not the voltage level, thus providing a perceptually accurate fade. The Effects Configure "Start Level" and "Stop Level" parameters let you specify the beginning and ending attenuation or amplification levels for fade operations. These levels are expressed in decibels.

      2. Effects Mix From

        3. The Effects Mix menu command lets you mix audio data from another file. With this feature, you can add in another sound track from another file, merging the sounds. Effects Mix is useful for adding background sound or music to your audio presentations.

        After selecting Edit Mix you will be presented with a dialog box that enables you to select the name of the file from which to retrieve sound and adjust the relative volume levels of each file.

        To select a file from the list of files, select "Browse" and double-click the file name with the mouse (or position the highlight bar and press enter). To specify a different directory, move the cursor to the directory box and enter the new search specification. You can specify the type of file by clicking the mouse on the "Format" button.

        By default, the relative volume level of each file is set to 50%. This will mix equal levels of each file into the final recording. Normally, the volume levels of the two files will sum to 100%. If you use values that sum to less than 100%, you will reduce the overall volume level of the resulting sound. If you use values over 100%, you will increase the overall volume level of the resulting sound.

        When you select a segment that is shorter than the "Mix From" sound, VFEdit only mixes sound for the segment requested. When you select a segment that is longer than the "Mix From" sound, VFEdit only mixes sound for the extent of the "Mix From" source.

      3. Effects Normalize

        4. Effects Normalize scans the selected audio segment and tries to set the maximum volume level "To" an ideal target level with a permissible number of "Over" exceptions. The ideal "To" level is the volume level that would be achieved if the signal were a perfectly symmetrical wave; the "Over" exceptions compensate for the fact that most real audio waveforms are not symmetrical. The "To" and "Over" settings may be changed using the Effects Configure menu.

        When you normalize a file, VFEdit sets the levels of the file to an optimum level based upon a theoretical ideal. If you normalize multiple files, one at a time, the end result will be that they are each equal to an ideal, thus they each equal each other. You may remember from your school mathematics that if A=Z and B=Z, then A=B. This is the same basic principle used for equalizing multiple files, one at a time.

        Use Effects Normalize to adjust the overall volume level of a file so that a group of files will sound roughly equal.

      4. Effects Reduce Noise

The Effects Reduce Noise menu command reduces the volume level of amplitude values that fall below a specified threshold. When you have a scratchy sounding segment, this feature can help to smooth out the extraneous sound. Effects Reduce Noise is useful for reducing certain types of background noise or hiss. The effectiveness of noise gate processing varies tremendously depending the nature of the noise, and the recording fidelity of the surrounding signal.

When you select Effects Reduce Noise, VFEdit reduces the volume level of all signals below a specified threshold. The threshold may be changed using the Effects Configure menu. This parameter is expressed as a percentage of the maximum amplitude possible with the current data format. Technically speaking, Effects Reduce Noise further attenuates the voltage level of any signal below threshold by the specified amount.

To determine the effectiveness of noise reduction processing on your recording, try this simple test:

Use File Save to save any changes you've made to your current file.
Select a portion of your file for the test. Play the audio segment unchanged.
Use Effects Reduce Noise to perform noise reduction processing. Play the selected segment again.
If you feel that noise reduction processing has improved the sound of your recording, save the file. If not, simply use File Revert to return to the original.
      1. Effects Tone Generator

The Effects Tone Generator command lets you insert Dual Tone Multi-Frequency signals (DTMF Touch-Tones) into a file. You might want to have special messages that you send to your answering machine at home to pickup your incoming messages. With the Effects Tone Generator you can splice voice messages and touch-tone codes together in the same outgoing message.

After selecting Effects Tone Generator you will be presented with a dialog box that enables you to specify the tone frequency, duration, and amplitude. This dialog box enables you to set the following parameters:

DTMF: Specify the pre-set touch-tone frequency to insert.
Amplitude: Specify tone signal level as a percentage of maximum. The default value of 80% should be appropriate for most applications.
Custom: Specify user-defined tones by frequency and amplitude.
Length: Specify the duration of the tone to 1/1000 of a second accuracy.

The default settings for amplitude and length will work well for most applications. Simply select the DTMF touch-tone you need to create. You can customize the DTMF frequencies for countries outside North America. See Appendix B, Configuration for more information.

After selecting "OK" from the Effects Tone Generator dialog box the new tone will be inserted at the point marked by the triangular "At Position" marker.

      1. Effects Volume Up, Down

        2. The Effects Volume Up and Effects Volume Down commands adjust the amplitude of the selected sound segment by the number of decibels that you have chosen in the Effects Configure dialog box.

        The Effects Volume Up, Down commands permanently change the loudness (volume level) of a previously recorded file. Use this command when an existing recording was too loud, or when a portion of a recording is not loud enough.

        Technically speaking, Effects Volume Up, Down increases or decreases the signal voltage by the specified decibel level.

      2. Effects Configure

        3. The Effects Configure menu lets you change effects parameters. After selecting Effects Configure, you will be presented with a dialog box that enables you to specify the parameters described below.

        1. Dynamic Compress/Expand

          2. The "Maximum" parameter limits the amount that the compressor/expander will increase or decrease the volume level of the audio. Increase this number (expressed in decibels) for a more noticeable effect.

        2. Echo

          3. The "Decay" setting specifies the decay attenuation level of the signal fed back into the original. The default level of -6 dB produces an intelligible, noticeable echo effect with minimal distortion. Other values produce different feedback levels for the decay attenuation. Positive values will produce distortion (the signal level will increase geometrically). Smaller negative values will produce a more noticeable echo effect while larger negative values will produce less noticeable effects.

          The "Delay" parameter specifies the time delay of the signal fed back into the original. The default time of .20 seconds produces an intelligible, noticeable echo effect with minimal distortion. Other values produce different feedback time delays. Smaller delay times produce a less noticeable echo effect, while larger delay times will produce more noticeable effects.

        3. Fade In

          4. The "Start Level" sets the volume level beginning point (in decibels) used when performing a Fade In operation. The default setting of -20 dB specifies that the volume level at the beginning of the fade will be 1/100th (dB = 10 log New/Old) of the of the original signal. This means that the volume level at the beginning of the fade will be nearly silent. Other values specify different beginning volume levels for the fade operation. Negative values specify that the beginning level should be quieter; 0 dB specifies that the level should be unchanged from the original; positive values specify that the beginning should be amplified.

          The "Stop Level" sets the volume level end point (in decibels) used when performing a Fade In operation. The default setting of 0 dB specifies that the volume level at the end of the fade will be the same as the original signal, i.e., unchanged. Other values specify different ending volume levels for the fade operation. Negative values specify that the end level should be quieter; 0 specifies that the level should be unchanged from the original; positive values specify that the end should be amplified.

        4. Fade Out

          5. The "Start Level" sets the volume level begin point (in decibels) used when performing a Fade Out operation. The default setting of 0 dB specifies that the volume level at the beginning of the fade will be the same as the original signal, i.e., unchanged. Other values specify different beginning volume levels for the fade operation. Negative values specify that the beginning level should be quieter; 0 dB specifies that the level should be unchanged from the original; positive values specify that the end should be amplified.

          The "Stop Level" sets the volume level end point (in decibels) used when performing a Fade Out operation. The default setting of -20 dB specifies that the volume level at the end of the fade will be 1/100th (dB = 10 log New/Old) of the original signal. This means that the volume level at the end of the fade will be nearly silent. Other values specify different ending volume levels for the fade operation. Negative values specify that the end level should be quieter; 0 specifies that the level should be unchanged from the original; positive values specify that the end should be amplified.

        5. Normalize

          6. The "To" level is the volume level that would be achieved if the signal were a perfectly symmetrical wave. This parameter is expressed as a percentage of the maximum amplitude possible with the current data format. The default value of 80% should be appropriate for most applications.

          The "Over" exceptions compensate for the fact that most real audio waveforms are not symmetrical. Allow the volume to go over target range some percentage of times in order to achieve a better overall level. Set this parameter to zero to force no portion of this signal to go over the target level.

        6. Reduce Noise

          7. The "Attenuation" parameter setting (expressed in decibels) is the amount that the volume level will be reduced by the Effects Reduce Noise command. Larger negative values will produce a more noticeable effect.

          The "Threshold" parameter sets the noise reduction threshold as a percentage of the maximum signal level. The default setting of 3% specifies that any signal below 3% of maximum will be reduced in volume. This level is useful for reducing many types of background noise with minimal distortion. Other values specify different threshold levels. A larger number increases the amount of reduction, but may introduce distortion; smaller values decrease the amount of noise reduction.

        7. Volume Up, Down

        The "Up" and "Down" parameters set the volume adjustment levels (in decibels) used when increasing or decrease the volume level of a previously recorded file.

        A value of 0 dB specifies that the volume level will remain the same. Negative values specify that the level should be quieter; positive values specify that the volume level should be increased.

      3. Working with decibels (dB)

        4. The decibel (dB) is a unit of measure for expressing the ratio between two amounts of electric voltages. The decibel is used because of the wide range in sensitivity of the human ear. In our usage one dB equals 20 times the common logarithm of the ratio of the old signal voltage versus the new signal voltage.

        Since the human ear is sensitive to the power of the signal, the intensity of the sound is equal to the square of the voltage level. Thus doubling the intensity of the sound means an increase of a little more than 3 dB.

        For example, an audio segment that is to be made four times as loud would increase by:
        dB = 20 * log(New Voltage/ Old Voltage)
        dB = 10 * log(New Power / Old Power)
        dB = 10 * log (4/1)
        dB = 10 * +.60
        dB = 6.0

        Similarly, an audio segment that is to be made one-fourth as loud would decrease by:
        dB = 20 * log(New Voltage/ Old Voltage)
        dB = 10 * log(New Power / Old Power)
        dB = 10 * log (1/4)
        dB = 10 * -.60
        dB = -6.0

      4. Using a Math Coprocessor

        5. Effects functions can benefit greatly from the use of a math coprocessor. VFEdit will automatically detect and use an 80287/80387 (or compatible) math coprocessor if one is installed. Similarly, VFEdit will automatically detect the presence of the coprocessor built into chips such as the Intel 80486DX or Pentium®.

        Fade and Volume effects will typically operate eight to twelve times faster with a coprocessor. The following benchmarks were made with a zero wait-state 10 MHz 80286 computer tested with and without an 80287 coprocessor. Here are the following times required for effects performed on a 128,000 byte file:

        Effect without coprocessor (sec) with coprocessor (sec)

        Noise Gate 11 11
        Volume Adjust 139 23
        Fade 349 46
        Echo 141 24

      5. ADPCM Effects

VFEdit performs an ADPCM to PCM conversion, then a PCM to ADPCM conversion during Effects operations. These algorithms have been designed and tested for mathematical symmetry. VFEdit minimizes the time-dependent side effects of ADPCM by performing a 1 second "Guard Time" calculation prior to any Effects operations. Best results can be achieved by positioning a zero or near-zero point at or before (within 1 second) the beginning point of the selected audio segment.

The Edit Erase operation does not use a guard calculation, and simply sets the ADPCM code to fixed +1, -1 sequence. This works well for the majority of audio segments. Audio segments with large amplitude variations, however, may require use of the Effects Fade and Effects Volume operations.

The ADPCM to waveform translator also includes a signal processing algorithm for DC rejection. This emulates the capacitive coupling of the actual hardware.